1. Field of the Invention
The present invention relates to a package substrate and a method of fabricating the same, and more particularly, to a package substrate capable of controlling the degree of warpage thereof by improving the composition and formation of a post terminal and a method of fabricating the same.
2. Description of the Related Art
A flip chip package has solder bumps formed on a chip and a substrate in contact with each other.
With an increase in data processing capacity and the trend for lighter, thinner, shorter and smaller semiconductors, a flip chip package used for high-speed large-capacity data processing has a gradually decreased bump pitch.
The change of the flip chip package under the above trend causes a problem of deteriorating bump reliability, and accordingly the improvement thereof is required.
Conventionally, in order to improve contact reliability between bumps formed on a substrate and a chip, the bump formed on the chip has been formed of copper having a greater mechanical strength and being more stable than solder and the bump formed on the substrate has been formed to have a copper post structure.
Solder is generally used for the contact between bumps formed on a chip and a substrate. The solder is printed or plated on a copper post formed on the substrate. However, such a copper post has some problems. The copper post is easily oxidized and has a great degree of hardness, so it is susceptible to cracking or short circuiting when warpage between the substrate and the chip occurs.
Accordingly, there has been an attempt to replace the copper post with various metallic alloys. However, when a post is formed of such a metallic alloy, separation between a metal seed layer and a dry film has occurred, and accordingly, an undesired plating of an insulating layer may be performed or a desired plating of a pad may not be performed.